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 (DIR) Return to: Restorations
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       #Post#: 53753--------------------------------------------------
       Twin cylinder double acting steam engine.
       By: Tony Bird Date: October 26, 2022, 7:55 am
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       Twin Cylinder Oscillating Engine. Part 1.
       The Cardiff Model Engineer Society during a year have several
       Bring & Buy Sales.  The rules are simple anything slightly
       inclined towards model engineering can be offered for sale and a
       small donation is made to the society. The only rule rigidly
       adhered to is that if not sold the items are taken away.  At the
       end of one sale among the items not sold was a rusty Huntley and
       Palmer biscuit box that was fully of very rusty metal and dirt;
       among which was a Heinz jar supposedly containing 6 BA steel
       screws.  Having run out of 6 BA screws on a job, and not yet
       ordered any, the biscuit tin and its contents were purchase for
       a nominal sum.
       The screws were indeed 6 BA and were used until the arrival of
       new ones.  As to the other contents of the tin; as well as rusty
       bolts, worn out tools, swarf, dirt and bits of newspaper there
       was treasure! There was a complete set of cast iron inside
       cylinder castings for a 3.1/2” gauge locomotive, a number of
       small flywheel castings and what is going to be played with; a
       twin cylinder double acting oscillating engine, a lot of which
       was missing.
       It will be a bit of a challenged deciding what the missing parts
       might have looked like, and indeed what sort of engine it was
       supposed to be.  Any suggestions on construction and what type
       of engine will be helpful. It is intended to work on the parts
       of the engine between other jobs as a sort of a fill in, this
       will give a bit of thinking time regarding the construction and
       appearance of the new parts.  First it has been decided to work
       through the original parts cleaning them up and doing any
       repairs that might be needed.
       The first part of what will be probably a protracted build is
       cleaning up and repairing the crank shaft.
       It is quite an interesting crankshaft, a bit like those used on
       a winch engine, it has heavy brass disc cranks with a 32mm
       (1.1/4”) stroke acting as flywheels along with a pair of
       aluminium pulleys on the shaft, for flat belts?  Between these
       pulleys the is a single bronze eccentric, for a water pump?
       The construction of the crankshaft is also a bit different; the
       disc cranks being riveted to short lengths of axle; these axles
       slide into the pulley/eccentric assembly, each being secured in
       place by a set screw.
       The crank pins were driven out of their crank discs using a
       punch and stake, the crank pins were different to each other one
       of them being smaller in diameter and having a brass sleeve.
       The parts of the crankshaft had their paint removed and were
       cleaned up and when assembled again with temporary set screws it
       was found that the cranks were set at about 80 degrees to one
       another!
       The reason for the angular error might be that original set
       screw holes in the pulley/eccentric assemble aren’t inline.  It
       was decided to drill new set screw holes at 90 degrees to the
       originals.  The original holes were threaded either 1/8”
       Whitworth or 5 BA, both screw types fitting loosely, the new set
       screws are M3.
       At end of play with the crankshaft, the disc cranks had been
       painted and new crank pins fitted. The pulley/eccentric assembly
       had new set screws and the cranks are set at 90 degrees.
       That is the first part of what might be considered a
       restoration/rebuild of a steam engine.  A week is to be spent in
       Wild West Wales and the pencil case and paper will be taken to
       try out some ‘What if’ ideas.
       Beginning of the day.  The parts of the engine found in the
       biscuit tin.
       [attachimg=1]
       End of the day. Finished crankshaft.
       [attachimg=2]
       Take care Tony.
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